This invention relates generally to can body manufacture and more particularly to an improved apparatus for providing precise cutoff control when cutting individual cans from an elongated body blank.
In the manufacture of spirally wound cans, roll stock of suitable body material is helically wound and bonded on a mandrel. This process is primarily utilized with composite body material and, after the continuous helical tube is formed, it is then cut into individual can bodies of appropriate length. The roll stock material is usually printed with the appropriate product labels prior to being helically wound and, of course, there is a repetitive printed copy. The can bodies, after they are cut from the elongated tube, then undergo further processing; for example, adding an end closure, filling, and adding the other end closure.
At least two methods are used for cutting the elongated tube into individual can bodies. One method is to first cut a long section of the continuously wound helical tube, referred to as a "stick," and then to cut the stick into shorter lengths. The other principal method is to substantially continuously cut individual can body lengths from the continuously wound tube. Of course, in either method the cutting must be in registry with the repetitive printed copy on the elongated tube.
An example of a typical can cutting system is disclosed in U.S. Pat. No. 3,942,418 issued to C. J. Smith and assigned to Container Corporation of America. Disclosed in the Smith patent is a winding mandrel on which the helically wound tube is formed together with a drive means for continuously moving the so-formed tube axially to the cutting station. At the cutting station, a knife carriage is operable which also travels axially with the tube. The knife carriage and traveling tube are synchronized so that cutting of the individual can bodies is effected.
A problem when cutting individual can bodies from elongated printed tubes using prior art methods is that the knives are not always precisely positioned so as to be in registry with the printing. In the past, one way to accommodate the problem has been the provision of planned waste referred to as a "scrap ring." It is usually necessary to cut a scrap ring each time the knives on the cutoff carriage are brought into the cutting position. Of course, it is recognized in the art that the necessity of providing a scrap ring increases the overall manufacturing cost. In addition, can bodies that are produced with the provision of a scrap ring typically have the printing (the resulting label) on each can off-centered (referred to as "floating copy") which leads to an aesthically unpleasing appearance when the can product is on the shelf of the retailer. This results when a knife carriage has a plurality of knives such as six whereby six can bodies are generated at once and the floating copy will be a part of each body when the knives are not precisely positioned. Oftentimes, if the rotary knives are not repositioned in a controlled manner for each succeeding cutting cycle, the floating copy will tend to be cumulative with cans being unacceptable since the printed copy will be completely off-center.
There are control systems in the prior art for spiral winding machines that are designed to cut individual can bodies from the elongated tube sections in good registration with the label copy. However, it has been found that these control systems require frequent adjustments so as to be synchronized with the label copy, requiring constant attention by an operator. This, of course, adds to the overall cost of the can manufacturing process.
Of course, it will be recognized by those skilled in the art that not only must the label copy be considered when cutting individual can bodies, but the knives on a moving carriage have the capability of cutting long or short can bodies, and this problem must also be considered. Long can bodies can be trimmed to size but a short can body is unacceptable.
Thus the primary purpose of the present invention is to precisely control the position of the elongated tube with its printed copy in relation to the cycling cutoff knives. If the desired relationship can consistently be maintained during operation, the provision of a scrap ring can be eliminated, thereby increasing utilization of the can body material while generating individual can bodies with well-centered labels. In addition, the precise control length, standards are consistently maintained. These and other objects of the present invention will be more fully understood and appreciated upon reading the specification to follow in conjunction with the attached drawings.